| Cactaceae | Cactus family |
| Campanulaceae | Bellflower family |
| Cannabaceae | Indian Hemp family |
| Caprifoliaceae | Honeysuckle family |
| Caryophyllaceae | Pink family |
| Celastraceae | Bittersweet family |
| Chenopodiaceae | Goosefoot family |
| Cistaceae | Rock-Rose family |
| Cleomaceae | Cleome family |
| Clethraceae | Clethra family |
| Colchicaceae | Meadow saffron family |
| Commelinaceae | Spiderwort family |
| Conocephalaceae | Conocephalum liverwort family |
| Convolvulaceae | Morning-glory family |
| Cornaceae | Dogwood family |
| Crassulaceae | Stonecrop family |
| Cucurbitaceae | Gourd family |
| Cupressaceae | Cypress family |
| Cyperaceae | Sedge family |